Trichomonas vaginalis is responsible for serious health consequences for women. Significantly, the infection by this parasite is a co-factor in amplifying the transmission of HIV among African American and Hispanic women contributing to poor minority health and health disparities in our nation. Fundamental aspects of Trichomonas cell and molecular biology remain unknown, despite the impact to public health. Our long-term goal is to understand the molecular basis of pathogenesis. Adherence of trichomonads to vaginal epithelial cells is important for infection, and, therefore, the objective of this proposal is to study the structure, function and regulation of T. vaginalis AP65 adhesin compartmentalization. The rationale for undertaking these studies is that more effective means of control of infectious diseases requires enhanced knowledge of the fundamental biological processes that govern virulence. The AP65 adhesin has sequence identity to malic enzyme (decarboxylating), an enzyme of organelles called hydrogenosomes. Thus, AP65 belongs to the category of surface-associated microbial enzymes with functional diversity. The hypotheses being tested are that i) iron regulates gene expression, compartmentalization and surface placement of all members of the ap65 gene family, ii) there is cross signaling by phosphorylation of trichomonads and AP65 following adherence, and iii) there is a quantitative relationship between host epithelial cell receptors for AP65 and levels of cytoadherence. Four aims are proposed. Aim 1 will show compartmentalization outside hydrogenosomes by expressing tagged-AP65 fusion in wild type and MR100 (AP65-negative) mutants. Aim 2 will determine the mechanism of ompartmentalization of AP65. Aim 3 will examine the differential binding of trichomonads to host epithelial cells mediated through AP65 and cell receptor. Finally, Aim 4 will silence expression of the ap65 genes. In addition to the biological merit, innovative aspects of our proposal are our use of antisense transfection to silence expression of ap65, and the use of drug resistant MR100 lacking hydrogenosome proteins (AP65-negative) to study adherence.